JPH046266B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention provides a method for enclosing a high-voltage secondary circuit with a metal body,
This product relates to a high-frequency heating device that prevents electric shock accidents due to high voltage on the secondary side by preventing contact with the power supply side, and has a double insulation structure for the live part on the power supply side, eliminating the need for grounding work. be.

Conventional technology In the unlikely event that insulation deteriorates between the high-voltage secondary circuit and the power supply side, and high voltage leaks to the accessible metal part of the hinge, the conventional high-frequency heating device (hereinafter simply referred to as a microwave oven) Provide a ground terminal on accessible metal parts,
The idea was to ensure safety by conducting grounding work to the ground, bypassing the electric shock current flowing through the human body, and reducing the electric shock current flowing through the human body to a safe level.

Problems to be solved by the invention However, if the above-mentioned high voltage leaks, 2
There were several problems, making it difficult to ensure safety.

The first issue is the extent to which grounding work will be carried out. Even if a microwave oven is equipped with a grounding terminal, grounding work must be done after the microwave is purchased, and there is a possibility that it will not be done for various reasons, making it difficult to ensure safety. In other words, in the case of high-rise condominiums, it is sufficient to have a grounding terminal installed at the outlet, but since only about 30% of them are currently equipped with this, in most cases the grounding wire is extended several meters or more than 10 meters. This method is not implemented due to the high cost of construction, as it requires a ground pole to be driven into the ground. In particular, it becomes increasingly difficult to carry out grounding work because it is necessary to redo the grounding work when transferring jobs or moving homes.

Also, even if you are not in a high-rise apartment building, you want to seal the aluminum windows, so you may have to make a hole in the wall for the ground wire to pass through, or if you try to drive it into the ground, it is difficult to drive the ground pole because it is made of concrete. Currently, there are many cases where grounding work is not carried out because there is no grounding work.
According to one survey, approximately 40 to 50% of microwave ovens are currently being used without being grounded.

Furthermore, if an earth pole were to be driven into the earth,
Even if grounding work has been done, the place where the grounding pole will be driven is dry or due to construction work.
If the ground surface is covered with gravel to improve drainage, grounding resistance will increase, making it impossible to ensure sufficient safety. On the other hand, the ground resistance value is approximately when a 50 cm carbon rod earth pole is driven into the ground.
It is possible to set the value to around 100Ω, but if a high voltage close to 2000V leaks, a leakage current of 20 amperes will flow, and considering the worst case scenario, if the human body resistance becomes around 500Ω, the human body The electrocution current that flows through the area can be as high as several amperes. Therefore, it is impossible to suppress the electric shock current to a value of 1 mA or less, which is said to be a safe level for the human body. There is also the possibility of corrosion of the ground electrode or breakage of the ground wire, so the conventional method of installing a ground electrode is a performance that ensures safety only on the premise of reliable grounding work. , it was extremely difficult to ensure safety against high voltage leakage of nearly 2000V.

Second, with the recent spread of microwave ovens, they have become lighter and more compact, and there is also a trend for microwave ovens that can be used not only on the table but can be moved freely. Conventional microwave ovens with ground terminals, which are fixed to the ground, are becoming inconvenient.

Means for Solving the Problems The present invention surrounds the high voltage secondary side circuit with a metal body,
In order to prevent contact with the power supply side, in addition to the metal chassis that houses the heating chamber and high-frequency generator, the core of the high voltage transformer, the metal case of the high voltage capacitor, the metal case of the magnetron oscillator, and the metal case of the high voltage transformer are placed on the chassis. The high-voltage secondary circuit is enclosed between the high-voltage secondary coil and the power supply-side primary coil through a metal wall formed by adding a cross-contact prevention plate that is electrically connected and fixed to the core. In addition, the primary coil on the power source side of the high voltage transformer and the components on the power source side have a double insulation structure.

Effect If the high-voltage insulator deteriorates due to the high-voltage secondary side circuit being enclosed with a metal wall and a current leakage occurs, one end of the high-voltage secondary side is connected to the chassis. A closed circuit is created within the circuit. This phenomenon is similar to when a high-voltage rectifier suffers dielectric breakdown, and the fuse in the power supply circuit blows to notify a failure state, just as in conventional ranges. Therefore,
Since insulation from the power supply side is maintained, cross contact will not occur.

In addition, since double insulation structure only requires measures for the primary coil and power supply circuit components, it is much easier to achieve than double insulation on the high-voltage secondary side, and the spatial distance between the chassis and the power supply circuit is much smaller. Since it is within 8mm between live parts, and 2.5mm if it is through an insulator,
This can be achieved without significantly increasing the conventional dimensions. As a result, there is no need for grounding work, and the location of use can be easily moved, compared to conventional methods that relied on uncertain grounding work.
It also becomes easier to ensure safety.

Embodiment Hereinafter, the configuration of a microwave oven according to an embodiment of the present invention will be described with reference to the drawings.

As shown in FIGS. 1a and 1b, a heating chamber 1 in which food is stored and cooked is equipped with a magnetron oscillator 2.
High frequency waves are emitted from the The high-voltage transformer 3 that drives the magnetron 2 is an insulating transformer that is divided into a power source coil 4 and a secondary high-voltage coil 5, and one end of the secondary high-voltage coil 5 is directly electrically connected to the metal chassis 6. has been done. The heating chamber 1 and the metal chassis 6 are connected by a fixing screw 22, and when this is removed, they are vertically separated. Therefore, the fixing screw 22 and
The plan view of FIG. 1 shows the heating chamber separated by removing the fixing screw 21 of the magnetron 2.

Core 7 is electrically coupled to metal chassis 6. Power supply side coil 4 and secondary high voltage side coil 5
A metal plate 8 is electrically coupled and fixed to the core 7 between the core 7 and the core 7.

As shown in the figure, the metal plate 8 constitutes a metal wall extending substantially perpendicularly from the core 7 and standing at right angles to the core 7, which has a sufficiently large height so that the power supply side coil 4 and the secondary high voltage side coil 5 cannot be seen through. are doing. The high voltage capacitor 9 is arranged on the chassis 6 such that the metal case constitutes one metal wall.

That is, in the embodiment, the high voltage circuit 10, including the high voltage diode 11, is surrounded by the transformer core 7 disposed on the chassis 6, the metal plate 8, the metal case of the high voltage capacitor 9, and the metal case of the magnetron 2, Furthermore, since the heating chamber 1 is enclosed in a metal case whose upper and lower sides are constituted by the bottom surface 12 and the chassis 6, there is no possibility that the live parts of the high voltage circuit will directly come into contact with the power supply side.

In this way, after placing the high voltage circuit 10 on the chassis 6 and wiring it from above, it is sufficient to cover the heating chamber 1 from above and tighten it with the fixing screws 22 and the fixing screws 21 of the magnetron 2. Various effects can be expected, such as eliminating the need for long high-voltage wiring, and eliminating the need to erect special metal walls.

In addition, the conduction of these metal walls is the magnetron 2
mounting screws 21, fixing screws 22 for heating chamber 1 and chassis 6, high voltage transformer 3, high voltage condenser 9
It is secured during each tightening operation by a fixing screw (not shown).

Next, the power supply side charging section includes the primary coil 4 of the high voltage transformer 3, the terminal section 15, and the fan motor coil 1.
6, the latch switch 17, the time switch 18, the power cord 19, and the power supply side low voltage wiring 20 correspond to this. A simple method for double-insulating these live parts on the power supply side will be described.

In FIG. 2, the primary coil 4 extends from the core 7 to a double insulation 24 consisting of basic insulation and additional insulation.
is shaped to extend from the core 7 by 8 mm or more, and a double insulation 23 consisting of basic insulation and additional insulation is provided on the primary coil 4 side of the metal plate 8. Returning to FIG. 1, the primary coil terminal 15 is provided on the side opposite to the high voltage secondary side terminal 13 from the power supply circuit side.

Referring to FIG. 3, a method for doubly insulating the power supply side low-voltage wiring 20 from the chassis and heating chamber will be described.
The fan motor bracket 25 to which the resin fan motor mounting plate and air guide are attached is provided with a flange 27 having a groove 26 in a direction perpendicular to the direction in which the low voltage wiring 20 is routed. for a given spatial distance, e.g. 2.4
mm or more. When wiring, pass the lead wire along this groove 26, and then connect it to the terminal 15 of the transformer primary coil 4 or the fan motor coil 16.
Insert it into the terminal. By managing and bundling the wiring with a small length margin so that the wiring does not come loose, the low voltage wiring 20 is always kept at a spatial distance of 2.4 mm or more from the metal wall of the upper heating chamber bottom 12 due to the flange 27. is retained. Therefore, by using the insulation coating of the low voltage wiring 20 as basic insulation and using the 2.4 mm spatial distance as additional insulation, double insulation can be achieved with a simple structure from the metal wall 12 and the chassis 6.

The fan motor coil 16 is attached to the fan motor bracket 25, and the latch switch 17 and time switch 18 are similarly attached to a resin production plate 28.
By attaching it to the metal wall 4, chassis 6
Also, the thickness of the specified insulation corresponding to the additional insulation from the surface of the part accessible from the outside (approximately 0.8 mm or more)
Alternatively, if the space distance (approximately 2.4 mm or more) is secured, basic insulation can be achieved while maintaining the conventional insulation specifications of the fan motor coil 16, latch switch 17, and time switch 18, so a double insulation structure is possible. can be realized relatively easily. Further, regarding the power cord 19, the insulation coating is made into a double sheath, so that basic insulation and additional insulation can be easily realized. The portion penetrating the metal chassis 6 is achieved by integrally molding a bushing made of vinyl chloride or the like with a thickness of about 1 mm or more on the double sheath.

Also, install an insulating holder 30 as appropriate to hold the power supply side low-voltage wiring in the air, and ensure a spatial distance of 2.4 mm or more from the metal wall and the chassis 6, or
Internal wiring that is already insulated with a PVC tube (0.4 mm or more) can be double insulated.

In either case, as long as the space is completely separated from the secondary high-voltage wiring, it is relatively easy to maintain the specified spatial distance using conventional parts using resin insulating mounting brackets and holders. In order to
Double insulation is easily achieved.

FIG. 4 shows a circuit diagram of the structure of the present invention. In the figure, if the high voltage secondary side suffers dielectric breakdown and a large amount of leakage current flows between the high voltage secondary circuit and the terminal connected to the chassis 6, the fuse 31 on the power supply side will be activated.

Effects of the Invention As described above, since the secondary high voltage side of the microwave oven of the present invention is substantially enclosed by a metal wall, even if the insulation on the secondary side deteriorates,
First, a leakage occurs between the metal wall and the shear ground point at one end of the secondary side, and the fuse in the power supply circuit blows in a short time. Therefore, there is no possibility of direct contact between the primary power source side and the secondary high voltage side, resulting in electric shock due to the secondary high voltage.

In addition, the secondary high voltage side is not enclosed by adding a special metal wall, but instead the conventional transformer core, high voltage capacitor, and magnetron metal case, and the metal plate installed on the high voltage transformer to prevent cross contact. Since the structure can be configured simply by devising the arrangement, the number of parts is reduced, and the secondary high voltage side can be prevented from coming into contact with the power supply side, and the length of the high voltage wiring can be shortened.

Furthermore, since double insulation is achieved with a relatively simple structure on the primary side, there is no increase in man-hours and the double insulation structure can be easily assembled, eliminating the need for grounding work for the range. It is extremely effective in practical terms, as it allows for easy movement and use.

[Brief explanation of drawings]

Figures 1a and b are a plan view of a chassis housing a high-frequency generator for a range according to an embodiment of the present invention, and a front cross-sectional view seen from the direction of the arrow in the plan view, and Figure 2 is a high-voltage transformer according to the present invention. FIG. 3 is a perspective view showing a fan motor bracket for double insulating the low-voltage internal wiring on the power supply side of the present invention, and FIG. 4 is a circuit diagram in an embodiment of the present invention. 1... Heating chamber, 2... Magnetron oscillator, 3
...High voltage transformer, 6...Metal chassis, 7...
Core, 8...Metal plate, 9...High voltage capacitor,
10... High voltage secondary side circuit, 11... High voltage diode.

Claims (1)

[Claims] 1. A heating chamber for storing and cooking food; a high-frequency generator for emitting high-frequency waves into the heating chamber;
a metal chassis that houses a high-frequency generator and shares a part of a metal wall adjacent to the heating chamber; a high-voltage transformer that electrically couples one end of the secondary side of the insulation transformer to at least one of the chassis or the transformer core; A high voltage capacitor having a metal case connected to the high voltage transformer secondary circuit and a magnetron oscillator also having a metal case are arranged on the metal chassis, and the high voltage secondary coil of the high voltage transformer and the power supply side primary coil are separated. The high-voltage secondary circuit is provided with a metal plate that is wound and directly connected and fixed to the transformer core between them, and the high-voltage secondary circuit is shared with the core of the high-voltage transformer, the metal plate, the metal case of the high-voltage capacitor, the metal case of the magnetron, and the heating chamber. By surrounding the metal wall with the metal chassis and electrically connecting these metal parts, the high voltage secondary side is substantially enclosed and separated from the power supply side charging part by the metal wall, and it can be separated from the power supply circuit. In addition to preventing cross-contact, the primary coil of the high-voltage transformer is double-insulated, and the power supply side parts are attached to a resin frame to prevent metal walls of the heating chamber, metal chassis, and high-voltage secondary circuit parts. A high-frequency heating device configured to insulate by maintaining a predetermined distance from the case, and at the same time maintain a predetermined distance from the parts touched by fingers from the outside.